Wheat crops are commonly affected by the dryland root rot complex (DLRRC) under dry and semiarid conditions. This complex is associated with seedling blight, and rotting of roots, crowns and stems of wheat plants. Several pathogens are associated with this complex, but Fusarium crown rot disease (FCR) is the most common and is of worldwide importance. Increased drought frequency and changes in rainfall regimes associated with global climate change may increase the prevalence of this complex of diseases, especially of FCR, in wheat crop areas. This review discusses the characteristics of the pathogen species involved in DLRRC, the known interactions between the pathogens, and information regarding management strategies. We also discuss the possibility that the activity of FCR pathogens could act as a sensor of global climate change

Seed treatments with antagonistic bacteria could reduce the severity of crown and root rot diseases in wheat crops. The objective of this study was to evaluate the potential antagonistic activity of a bacterial consortium of three Chilean strains of Pseudomonas protegens against the wheat crown and root rot pathogens Gaeumannomyces graminis var. tritici, Rhizoctonia cerealis, and Fusarium culmorum. Two field experiments were carried out on artificially infested soil during two consecutive seasons (2016–2017 and 2017–2018) in an Andisol soil of southern Chile. Control treatments (not inoculated with fungi) were also included. Each treatment included a seed treatment of spring wheat cv. Pantera-INIA with and without the bacterial consortium. Both phytosanitary damage (incidence and severity) and agronomic components were evaluated. Bacterial populations with the phlD+ gene in the wheat plant rhizosphere during anthesis state (Z6) were also quantified. In both seasons, infection severity decreased by an average of 16.8% in seeds treated with P. protegens consortium, while yield components such as spikes m⁻¹ and number of grains per spike increased. The use of antagonistic bacteria resulted in a total yield increase only during the first experimental season (P < 0.05). In general, accumulated rainfall influenced the antagonistic effect of the consortium of P. protegens strains, accounting for the differences observed between the two seasons. The results suggest that this P. protegens consortium applied on seeds can promote plant growth and protect wheat crops against crown and root rot pathogens in Southern Chile under field conditions.

Huanglongbing (HLB) is one of the world’s worst diseases of citrus trees. The research was conducted to characterize positive citrus samples of two local varieties, ‘Kinnow’ mandarin (Citrus reticulata Blanco) and ‘Mosambi’ orange (C. sinensis (L.) Osbeck), based on morphological, physical and biochemical characters. Physical and biochemical parameters of greening infected and healthy samples of both the cultivars were significantly different. Citrus fruits were lopsided and half to full green in the HLB infected trees compared to healthy. The HLB infected leaves samples were small and narrow. Fruit diameter, leaf area, and juice weight of HLB infected samples were significantly less than healthy samples. The rind thickness of infected fruits (70% and 80%) was significantly higher than healthy ones (20% and 30%). Starch content of leaves from mandarin (5.54 μg mL^-1) and orange (6.12 μg mL^-1) were significantly higher in HLB infected plants, while juice percentage of HLB infected fruit samples was lesser in mandarin and orange (22.73%, and 14.70%, respectively) than healthy fruits (38.22% and 31.30%, respectively). Acidity was significantly increased in juice of HLB infected mandarin and orange fruits (0.57%, and 0.53%, respectively). Similarly, there was significant reduction in biochemical parameters; total sugars in mandarin and orange (5.16% and 4.79%), total soluble solids (8.54% and 8.28%), total chlorophyll (13.50 and 14.92 mg mL^-1) and ascorbic acid (34.28% and 34.12%) in HLB infected samples of both cultivars. This study determined differences of physical and biochemical parameters of two local citrus varieties, commonly cultivated in the Asian region.